Magnetic recording head



NOV. 25, 1947. c s 2,431,541

LEI E172 0r Marvin 6km ms Patented Nov. 25, 1947 MAGNETIC nnoonnmo HEADMarvin Camras, Chicago, Ill., assignor to Armour I Research Foundation,Chicago, 111., a corporation of Illinois Application May 31, 1945,Serial No. 596,916

This invention relates to a magnetic recording head and moreparticularly to a head which may be employed to magnetically recordfluctuating electric energy on an elongated traveling record medium, andto reproduce electrical fluctuation from a previously magnetized recordmedium.

One of the principal features and objects ofthe present invention is toprovide a novel magnetic recording head which will approximate the samehigh quality recording and reproduction which is obtained by using ahead having a traveling record medium pass directly through the voicecoil, but which employs, in this case, an ar rangement in which the headmay be placed into a position against the traveling record medium andmoved away therefrom at any time.

More particularly, this is an improvement over my copending applicationentitled Magnetic recording head, U. S. Serial No. 580,605, filed March2, 1945, and assigned to the same assignee as the present invention.

It is one of the objects of the present invention to provide a novelrecording and reproducing head of an improved open slot type.

his a further object of the present invention to provide a core piece ofnovel construction for a magnetic recording and reproducing head.

Another and further object of the present invention is to provide anovel recording head in which the greater part of the recording head isat substantially zero M. M. F.

7 Another and still further object of the present invention is toprovide a recording head having the electric recording or pickup coilwound thereon in a novel manner.

Still another and further object of the present invention is to providea novel method and means for magnetizing a traveling elongated recordmedium and for reproducing electric energy from a previously magnetizedrecord medium.

A still further object of the present invention is to provide a novelhigh fidelity recording and reproducing head including pole piecesconstructed in a novel manner.

The novel features which I,believe to be characteristic of my inventionare set forth with particularity in the appended claims. My inventionitself, however, both as to its organization, manner of construction andmethod of operation, together with further objects and advantagesthereof, may best be understood by reference to the accompanyingdrawing, in which:

Figure 1 is a front elevational view of the core member of a recordinghead embodying the novel features of the present invention;

7 Claims. (Cl. 179-1002) Figure 2 is an end view of the core membershown in Figure 1;

Figure 3 shows the recording head, including the core piece, as shown inFigures 1 and 2, together with the core wound in place thereon prior totheinsertion or certain non-magnetic wire guide blocks; and

Figure 4 is a view similar to Figure 3 but with the wire guide blocks inplace and a traveling record medium in operative association therewith.

Referring first to Figures 1 and 2 of the drawing, I have illustratedthereby the paramagnetic core structure of one embodiment of the presentinvention. More particularly, I have shown in Figures 1 and 2 a corepiece l0 which is preferably made from a stamping of some suitableparamagnetic material having a relatively high initial permeability. Asthe expression initial permeability is used herein, it refers to thepermeability of the material at relatively low values of the excitingfield. In other words, a material having relatively high initialpermeability is a material having rapidly increasing values of magnetismfor small incremental increases of field strength at relatively lowvalues of field strength.

The stamping or core piece l0 includes a base portion H and twoconfronting polar portions i2 and i 3. The confronting polar portions l2and 13 are formed by stamping a generally triangular shape opening it inthe core ill and by cutting out upper notches l5 and is as shown. Thisleaves the confronting polar portions l2 and 13 with upstanding tonguesii and it. The edges of these upstanding tongues l1 and i8 are cut backas at l9 and 20 in the manner shown in Figure 1.

The upper corners 2i and 22 are grooved as at 23 (see Figure 2), as arealso the pole tips I1 and I8. This groove 23 lying in the cornerportions 2| and 22 and the pole tips H and iii are arranged to receiveand guide a traveling record medium such, for example, as a steel wire24 (see Figure 4).

Referring now to Figure 3, it will be apparent that a number of turns ofwire (such. for example, as insulated copper wire) are wound on thepolar portion I2 as at 25 and on the polar portion l3 as at 26. The wireforming the coil 26 is a continuation of the wire forming the coil 25and is wound in the same direction. In effect, the coils 25 and 26 arelike a single solenoid or helically wound coil with adjacent turns ofthe coil near the center spread apart but still electrically con nectedto each other. The outer end of the coil 25 terminates in a leadconductor 2'! and the outer end or the coil 2! terminates in a leadconductor to the upper corner portions 2! and 22 and the pole tipportions l1 and IS in any suitable manner, such as soldering, cementing,pinning, or the like. The blocks 30 and II are also notched for thereception of the traveling record medium 24 in the same manner as werethe upper edges of the corners 2| and 22 and the pole tips I! and it.The blocks 30 and 3| also are provided with an arcuate upper edge whichforms a continuation of the upper edge of the corners 2i and 22 and thepole tips I1 and 22. This, in effect, will provide a crowned edge forthe portion of the magnetic head which receives the traveling recordmedium.

While the blocks 30 and 3| may be formed of any suitable non-magneticmaterial, by way of example it may be said that they may be formed ofbrass or some other relatively hard non-magnetic material which willserve as the principal bearing surface for the traveling wire 24.

Considering. now the eiTect of the operation of the recording andreproducing head when acting in its recording capacity, let it beassumed that at some given instant of time current is flowing up throughlead conductor 21 and down through conductor 28. This will produce anorth pole at the left-hand end of the coil 25 and a south pole at theright-hand end of the coil 25. It will also produce a north pole at theleft-hand end of the coil 26 and a south pole at the right-hand end ofthe coil 26. This produces a very strong concentration of flux acrossthe gap between the pole tips l1 and IS. The return path for the flux isthrough the relative large mass of the base portion i i. Due to thepresence oi the non-magnetic blocks 30 and 3| there is substantially noreturn path in the region above the coils 25 and 28. This, then, meansthat substantially the entire M. M, F.

drop in the magnetic circuit is across the relativehead is substantiallyat zero M. M. F. Upon careful consideration of this, it will be seenthat substantially the same eflect is obtained with this type of corestructure and magnetic head as would be obtained by mounting an excitingcoil on a core piece having a hole extending axially therethrough andrunning the record medium directly through this axially extending holein the center of the exciting coil.

The impedance of the magnetic head may be varied by varying the numberof turns of wire in the coils 25 and 2B and the winding may be in theform of a single layer or a plurality of layers, depending upon theimpedance desired.

When the magnetic head is being used for reproducing, it will operatewith equal efiiciency, for the magnetized record medium travelingbetween the pole tips I! and I8 will induce a fluctuating current in thecoils 25 and 26 which is a function of the recorded fluctuation on therecord medium.

Due to the simplicity oi the core structure. it will further be observedthat this magnetic head is extremely economical to manufacture and byits open slot construction is extremely practical and easy to use, forit is simply neeessaryto move any intermediate portion oi the travelingrecord medium 24 into position in the wire guiding slot 22 o! the head.

While I have shown a particular embodiment oi my invention, it will, ofcourse,-be understood that I do not wish to be limited thereto sincemany modifications may be made, and I, therefore, contemplate by theappended claims to cover all such modifications as fall within the truespirit and scope of my invention.

I claim as my invention:

1. A magnetic head for recording and reproducing comprising a coremember having a pair 01' polar portions extending toward each other.each polar portion having a toe portion extending generally laterally tothe general direction 01' extension of the main body of said polarportion, said toes lying in close proximity to each other and having anon-magnetic region therebetween, magnetizing and reproducing coilswound over said main body portions of said polar portions, said headhaving means ior guiding a traveling record medium alongside of one ofsaid coils, over first one and then the other oi said toes and thenalongside of said other coil, the region between said traveling recordmedium and said coils being main body portions 0! said polar portions,said head having means for guiding a traveling record medium over one ofsaid heels, then alongside of one of said coils, then over said toeportions successively, then alongside the other of said coils, and thenover the other heel.

3. A magnetic head for recording and reproducing comprising a. coremember having a pair of polar portions extending toward each other, eachpolar portion having a toe portion extending generally laterally to thegeneral direction of extension of the main body of said polar portion,said toes lying in close proximity to each other and having anon-magnetic region therebetween, magnetizing and reproducing coilswound over said main body portions of said polar portions, said headhaving means for guiding a traveling record medium alongside of one ofsaid coils, over first one and then the other of said toes and thenalongside of said other coil, said head having non-magnetic portionsbetween said path of travel of said record medium and said coil, saidnon-magnetic portions including means for guiding the record medium oversaid head to and away from said toe portions.

4. A magnetic head for recording and reproducing comprising a coremember having a pair of polar portions extending toward each other, eachpolar portion having a toe portion extending generally laterally to thegeneral direction of extension of the main body oi said polar portion,said toes lying in close proximity to each other and having anon-magnetic region therebetween, said polar portions also having heelportions spaced from said toe portions and extending in the samedirection as said toe portions, magnetizing and reproducing coils woundover said main body portions of said polar portions, said head havingmeans for guiding a traveling record medium over one of said heels, thenalongside of one of said coils, then over said toe portionssuccessively, then alongside the other of said coils, then over theother heel, said head including non-magnetic members between the heeland toe of each of said polar portions, said means for guiding saidtraveling record medium including in part said non-magnetic members.

5. A magnetic head for recording and reproducing comprising a coremember having a pair of polar portions extending toward each other, eachpolar portion having a toe portion extending generally laterally to thegeneral direction or extension of the main body of said polar portion,said toes lying in close proximity to each other and having anon-magnetic region therebetween, said polar portions also having heelportions spaced from said toe portions and extending in the samedirection as said toe portions, magnetizing and reproducing coils woundover said main body portions of said polar portions, said head havingmeans forguiding a traveling record medium over one of said heels, thenalongside one of said coils, then over said toe portions successively,then alongside the other of said coils, then over the other heel, saidhead includ ing non-magnetic members between the heel and toe of each ofsaid polar portions, said means for guiding said traveling record mediumincluding in part said non-magnetic members, said nonmagnetic memberslying between the path of travel of said record medium and said coil.

6. A magnetic head for recording and reproducing comprising a plate ofrelatively high mag netic permeability and relatively low magneticretentivity, a groove extending along one edge of said plate forreceiving and guiding a traveling record medium, said plate having anon-magnetic gap therein extending inwardly from said one edge, saidplate having a pair of slots in close proximity to said one edge onopposite sides of said gap, said plate having at least one additionalopening therein, and a magnetizing coil wound through said slot fromsaid additional opening, the coil being wound the same way on both sidesof said gap, whereby the adjacent ends of the coil portions on oppositesides of saidgap are of opposite magnetic polarity, said plate beingformed of non-magnetic material in the region between said groove andsaid coil.

'7. A magnetic head for recording or reproducing comprising a coremember, means for guiding. a traveling record medium over apredetermined path, at least three apertures in said core member, thefirst and second of said apertures being located in close proximity tosaid path of travel of said record medium, said core member having anon-magnetic gap between said first and second apertures, and arecording and reproducing coil wound partly through the first and partlythrough the second of said apertures and the additional apertures, theregion lying immediately between the path of travel of said recordmedium and said coil part being non-magnetic, but all of the remainingportion of said plate being formed of a material of relatively highmagnetic permeability and relatively low magnetic retentivity, includingthe portions immediately adjacent and on either side of saidnon-magnetic gaps.

MARVIN CAMRAS.

REFERENCES; (HTED The following references are of record in the file ofthis patent;

UNITED STATES PATENTS Number Name iDate 2,351,007 Camras June 13, 1944FOREIGN PATENTS Number Country Date 805,434 France Nov. 19, 1936 322,033Great Britain Nov. 28, 1929

